Worms in sardine cans present a kosher quandary

Some 21st century technology has come to the aid of 2000-year-old religious dietary laws. Orthodox Jewish rabbis in New York recently called in DNA experts to help them answer an unusual question: Are worms found in a sardine can kosher?

Let’s say one day you’re opening up a can of sardines and you come across a worm. It is not as unusual as you might think.

“Unfortunately, recently, it hasn’t been unusual at all,” noted Rabbi Chaim Loike with the Orthodox Union, an organization that certifies whether products conform to Jewish dietary law. Loikea says these worms were showing up in about one out of every six cans. He does not know why they have become so common, but he says it is not necessarily a new phenomenon.

“The Talmud, which was written 2,000 years ago, described a number of worms, which, even though they’re not something you would want to eat, if they were accidentally consumed, would be kosher,” Loikea explained.

The Talmud, a compilation of rabbinic opinions, debates and analyses, lays out the framework for Jewish law. It says if the worm comes from the intestines, it is generally not kosher.

“However, if a worm is found to have grown its entire life in the flesh of the fish, it is considered to be the same as the fish,” said Loikea. “And therefore, it’s kosher.” Intestinal worms might show up if the sardines are not handled properly.

But why would it matter if the worm is kosher? Most people would still find it disgusting.

Well, if the rabbis decide that these worms, which have become so common in sardines, are not kosher, the Orthodox Union would no longer give the fish its seal of approval. That’s a big deal, because even many non-Jews look for that certification as a sign of quality. Kosher foods are a $12.5 billion market.

“We’re not advocating that people should eat worms. We’re just researching whether or not we would have to de-certify all these things,” Loikea added.

But Loike is a rabbi, not a parasitologist. He can’t tell a gut worm from a flesh worm. So he went where anyone would go to find an expert: the Internet search engine, Google.

“And we saw all the names of people who published papers on them and we started cold-calling them,” said Loike.

Mark Siddall at the American Museum of Natural History in New York is one of the world’s top experts on parasites. Siddall invited Loike to his office. The rabbi came with some cans of sardines, some tubs of fish eggs.

“[He also brought] a bag of previously frozen whole sardines, as well, that were dripping on the floor as we were walking to the elevators,” recalled Siddall.

To figure out what kind of parasites Loike’s fish had, Siddall used a technique called DNA barcoding. The genetic code of certain genes varies enough between species that researchers can use them to tell one from another.

When he DNA-barcoded Loike’s sardine worms, he found five species.

“And in all cases they were species we would normally expect in the muscle tissue or the ovarian tissue of the fish, and thus there was no indication whatsoever that there was improper handling,” Siddall explained.

So the Orthodox Union issued a decision: the sardines remain kosher.

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